Lubricating composition consisting of perarylated silanes and solid lubricant powders

ABSTRACT

HIGH TEMPERATURE LUBRICANTS COMPRISING HOMOGENEOUS MIXTURES OF 10 TO 90 PERCENT BY WEIGHT OF PERARYLATED SILANES WITH 90 TO 10 PERCENT BY WEIGHT OF SOLID MOS2, GRAPHITE, BN, ALUMINUM POWDER, OR LOW MELTING GLASS. THE COMPOSITIONS DISCLOSED HEREIN HAVE UTILITY IN MEETING THE ELEVATED TEMPERATURE LUBRICATION REQUIREMENTS OF THE METALWORKING INDUSTRY.

United States Patent Ofice 3,575,858 LUBRICATING COMPOSITION CONSISTING OF PERARYLATED SILANES AND SOLID LUBRI- CANT POWDERS Attwell M. Adair and Leonard Spialter, Dayton, Ohio, assignors to the United States of America as represented by the Secretary of the Air Force No Drawing. Filed May 20, 1969, Ser. No. 826,260 Int. Cl. C10m 3/44, 5/26 US. Cl. 252-26 8 Claims ABSTRACT OF THE DISCLOSURE High temperature lubricants comprising homogeneous mixtures of 10 to 90 percent by weight of perarylated silanes with 90 to 10 percent by weight of solid M08 graphite, BN, aluminum powder, or low melting glass. The compositions disclosed herein have utility in meeting the elevated temperature lubrication requirements of the metalworking industry.

BACKGROUND OF THE INVENTION (1) Field of the invention This invention relates to a composition of matter useful in the field of lubricants.

(2) Description of the prior art In the field of lubricants it is impossible to predict whether any two or more components which might be combined to form a lubricant will be compatible and form a useful lubricating material. That is, even though each of two different chemical materials may be well known to have excellent characteristics as lubricants or as components of lubricants, one must still actually experiment in order to determine if the two different chemical materials may be used together as a mixture and if the mixture will prove to be even as good a lubricant as the separate entities by themselves are. The difiiculty in predicting stems in part from the fact that any two or more chemical compounds, when placed together, may react chemically with each other or together with contacting surfaces. Moreover, even though the chemical components may be inert at room temperature they often react chemically at the elevated temperatures of operation to adversely affect their utility. On the other hand, one of the components may separate and sink to the bottom or rise to the top of a mixture and thus defeat the purpose of the mixture.

Even if two (or more) lubricating components are found to be chemically and physically compatible there are other factors to be considered before a mixture of the two (or more) can be considered useful as a lubricant. For example, in the field of metalworking there are many commercially available lubricants. Each of these lubricants has its own special limitation which makes it not quite as desirable a lubricant as it should be. Some good commercially available lubricants form undesired residue buildups on the metal being worked. Some have short pot life. Most decompose while in use and may give 01f noxious fumes and/or constitute a fire and explosion hazard. Some dont adequately wet the metal being worked to provide the desired lubrication. These are representative of reasons why the previously available lubricants have been found wanting in some respect or other in the metalworking field.

Optimum lubrication with presently available lubrication systems prohibit the use of metalworking tooling temperatures greater than about 500 F. even though current tooling can easily sustain operating temperatures of 800 Patented Apr. 20, 1971 F. Higher tooling temperature than the presently available 500 F. is considered to be an important factor in working with such materials as nickel-base super-alloys, which characteristically have a narrow working temperature range, and titanium alloys which have a strong tendency to seize. In particular, the demand for production of high quality titanium tubing, wherein seizing is a serious limiting factor, is increasing at a rapid rate. The most efficient means of manufacturing tubing is considered to be drawing, and the most desirable drawing temperature for alpha-beta titanium alloys is 800 F. The lack of a satisfactory lubricant at this temperature has required less elficient means of tube manufacture to be used in order to obtain the desired product.

SUMMARY OF THE INVENTION The unexpected and a priori unpredictable properties of the new blended lubricants of this invention now make metal-working tooling operations at temperatures up to and including 800 F. possible. The lubricants disclosed herein all have fire points of greater than 800 F. and do not burn or decompose during use at temperatures up to 800 F. The lubricants of this invention, since they do not decompose at temperatures up to 800 F., may be used under continued service condition, which is not the case with the best of the prior art materials.

The blended lubricating materials of this invention consist of mixtures of perarylated silanes and such solid lubricants as molybdenum disulfide, graphite, boron nitride, aluminum powder, or low melting glass powder. Specific composition ranges and methods for forming the blends are described in detail in the following description of the preferred embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The lubricants of this invention may be prepared by a number of different methods.

(1) A perarylated silane and a solid lubricant powder may be ground together.

(2) A perarylated silane may be melted to a liquid and solid lubricant powder stirred in.

(3) Molten perarylated silane may be added to and stirred into solid lubricant powder.

(4) Perarylated silane may be dissolved in a solvent which is more volatile than the silane. Then solid lubricant powder may be added to the solution and the solvent evaporated.

Specific examples of perarylated silanes which may be used in practicing this invention are: phenyl-tris-(4-biphenylyl) silane, hexaphenyldisilane, tetrakis-(4-biphenylyl)silane, tetra-Z-thienylsilane, phenyltri-Z-thienylsilane, and 3-pyridyltriphenylsilane. Specific examples of solid lubricants are molybdenum disulfide powder, graphite powder, boron nitride powder, low melting glass powder, and aluminum powder. The two classes of components (silane and solid powder) form compatible, useful lubricants when blended into compositions having weight ratios of solid to silane ranging from 10 to 10:90, inclusive. The weight ratio of solid to silane may be selected for the performance characteristics desired.

The term perarylated silanes, as used in this specification, may be defined as that class of molecules constructed from silicon atoms and aromatic or substituted aromatic moieties. The aromatic moieties may be selected from carbocyclic or heterocyclic groups either alone or mixed. Specific examples are, of course, given above.

The following are specific examples of lubricant preparations carried out.

3 EXAMPLE I Powdered graphite was blended with phenyl-tris-(4- biphenylyl)silane. For this purpose, a measured amount of the silane was heated in a container to a temperature in the range from 320 F. to 500 F. Phenyl-tris-(4-biphenylyDsilane melts at about 320 F. and is a low viscosity liquid. The temperature of the molten silane was maintained and a measured amount of powdered graphite, 150325 mesh, stirred in. Complete blending resulted with ease. The consistency of mixtures prepared in this manner varied from stiff putty-like to thick soup-like depending on the ratio of graphite to silane. The mixtures solidified to glass-like texture upon cooling. They softened to their original consistencies when reheated. Graphite did not tend to settle out except when high weight percentages of silane were mixed with coarser graphite powder. The mixtures could be cooled and heated many times with no apparent change in characteristics. Compositions prepared in this way were 40 weight percent phenyl-tris-(4-biphenylyl)silane to 60 weight percent graphite, 50 weight percent of the silane to 50 weight percent graphite, and 60 Weight percent of the silane to 40 weight percent of the graphite.

EXAMPLE II Technical fine molybdenum disulfide powder was mixed with phenyl-tris(4-biphenylyl)silane. The mixing procedure of Example I was used. Consistencies and characteristics of the silane-M08 mixtures were similar to those of the silane-graphite mixtures of Example I except M08 did not tend to settle out even when high weight percentages of silane were used. Lubricants consisting of the following percentages by weight were prepared: (l) 30% of the silane to 70% M05 (2) 50% of the silane to 50% M08 and (3) 90% of the silane to 10% M08 EXAMPLE III Technical fine molybdenum disulfide powder was added to tetrakis-(4-biphenylyl)silane. To prepare such compositions, the silane was placed in a container and the container heated to a temperature in the range from about 540 F. to about 700 F. Tetrakis-(4-biphenyl) silane melts at about 540 F. and, like the silane of Examples I and II, is, when melted, a low viscosity liquid. After the silane was melted, powdered M05 was added to and stirred into the silane. A 50-50 by weight mixture was prepared. Upon cooling, the composition solidified to a crystalline form rather than to the amorphous (glass-like) form of the mixtures of Examples I and II. However, upon reheating and recooling, the material solidified into an amorphous form. The mixture exhibited no visible change in consistency at working temperatures.

EXAMPLE IV Phenyl-tris-(4-biphenylyl) silane was mixed with boron nitride and with aluminum powder in the same manner disclosed by Example 1. Materials and compositions were (weight percentages): (l) 67% of the silane to 33% boron nitride powder and (2) 67% silane to 33% aluminum powder. The mixing with BN required crushing to eliminate lumps in the boron nitride.

EXAMPLE V Blends of various perarylated silane-solid lubricant mixtures were prepared. The blends were prepared by heating one mixture in a container until a smooth con sistency resulted, adding a second mixture, and stirring. Blends prepared were (weight percentages): (1) 50% of 50% phenyl-tris-(4-biphenyl)silane-50% graphite with 50% of 50% phenyl-tris-(4-biphenylyl)silane-50% molybdenum disulfide, (2) a 50/50 mixture of 50% tetrak-is-(4- biphenylyl)silane-50% molybdenum disulfide with 50% phenyl-tris-(4-biphenylyl)silane-50% molybdenum disul- 4 fide, (3) a 50/50 blend of 50% phenyl-tris-(4-biphenylyl) silane-50% M08 and 67% phenyl-tris-(4-biphenylyl) silane-33% BN, and (4) a 50/50 blend of 50% phenyltris-(4-biphenylyDsilane-SO% MoS with 67% phenyl-tris- (4-biphenylyl)silane-33% Al powder.

EXAMPLE VI Other preparation methods were used. Mixtures of perarylated silanes such as hexaphenyldisilane, tetra-2- thienylsilane, phenyl-2-thienylsilane, and 3 pyridyl-triphenylsilane were blended with M05 graphite, aluminum powder, powdered low melting glass, or boron nitride by grinding in a mortar (or by grinding in another suitable manner such as in a ball mill) and heated to temperatures on the order of about 500 F. All such combinations were almost immediately fused by the melting action of the perarylated silane and appeared to have the same characteristics as mixtures prepared according to the methods of Examples I through V above.

EXAMPLE VII Equal mixtures by weight of powdered M08 and hexaphenyldisilane were heated on a hot plate and stirred together. The mixture wa then allowed to freeze. A portion of the frozen mixture was remelted and powdered phenyltris-(4-biphenylyl)silane was added and stirred into the melt. Both portions (the mixture of M03 and hexaphenyldisilane and the (mixture of M08 hexaphenyldisilane and phenyl-tris-(4-biphenylyl)silane) exhibited excellent lubricating properties for metalworking operations.

EXAMPLE VIII Approximately equal weights of powdered graphite and phenyl p biphenylyl-bis-(p-bromophenyl)silane were mixed by melting the silane, adding the graphite and stirring.

EXAMPLE IX Approximately equal weights of powdered molybdenum disulfide and triphenyl-2-thienylsilane were blended in a test tube and heated.

Performance evaluation The lubricating properties of compositions of this invention were evaluated during extrusion tests and compared with those of the best prior art lubricants. The 50-50 weight percent molybdenum disulfide-phenyktris- (4-biphenylyl)silane mixture gave the lowest values of container liner friction at 800 F. that have been obtained to date for extrusion operations under such conditions.

We claim:

1. A lubricating composition comprising a blend of (1) a perarylated silane having a structural formula selected from the group consisting of Sl(R R2R R4) and wherein R R R R R and R are selected from the group consisting of carbomonocyclic and dicyclic aromatic moieties, heterornonocyclic nitrogen or sulfur containing aromatic moieties, and mixtures thereof; and (2) a powder selected from the group consisting of molybdenum disulfide powder, graphite powder, boron nitride powder, glass powder, and aluminum powder, wherein from about 10 to about weight percent of said blend is said perarylated silane.

2. A lubricating composition comprising a blend of two components, the first component being selected from the group consisting of phenyl-tris-(4-biphenylyl)silane, hexaphenyldisilane, tetrakis-(4-biphenylyl)silane, tetra-2- thienylsilane, phenyltri-2-thienylsilane, and S-pyridyl-triphenylsilane; the second component being selected from the group consisting of the powders of molybdenum disulfide, graphite, boron nitride, low melting glass, and aluminum; wherein from about 10 to about 90 weight percent of said blend is said first component.

3. A composition of matter according to claim 2 wherein said first component is phenyl-tris-(4-biphenylyl)silane and said second component is powdered graphite.

4. A composition of matter according to claim 2 wherein said first component is phenyl-tris-(4-biphenylyl)silane and said second component is powdered molybdenum disulfide.

5. A composition of matter according to claim 2 wherein said first component is tetrakis-(4-biphenylyl)silane and said second component is powdered molybdenum disulfide.

6. A composition of matter according to claim 2 wherein said first component is phenyl-tris-(4-biphenylyl)silane and said second component is boron nitride powder.

7. A composition of matter according to claim 2 wherein said first component is phenyl-tris-(4-biphenylyl)silane and said second component is aluminum powder.

8. A lubricating composition comprising a blend of (1) at least two perarylated silanes selected from the group represented by the formulas:

Si(R1R2R R4) and wherein R R R R R and R are selected from the group consisting of carbomonocyclic and dicyclic aromatic moieties, heteromonocyclic nitrogen or sulfur-containing aromatic moieties, and mixtures thereof; and (2) at least one powder selected from the group consisting of molybdenum disulfide, graphite, boron nitride, low melting glass, and aluminum, wherein from about 10 to about 90 weight percent of said blend is said perarylated silanes.

References Cited UNITED STATES PATENTS 573,120 3/1896 Wheeler 25229 2,466,642 4/1949 Larsen 25229 2,894,969 7/1959 Pierce 25229 3,059,769 10/1962 Frost 25229 DANIEL E. WYMAN, Primary Examiner I. VAUGHN, Assistant Examiner UJS- Cl. X.R. 

